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Background
Published in Russ Martin, Sound Synthesis and Sampling, 2012
FM is the technical term for the way that FM radio works, where the audio signal of music or speech is used to modulate a high-frequency carrier signal which then broadcasts the audio as part of a radio signal. In audio FM, both signals are at audio frequencies, and complex frequency mirroring, phase inversions and cancellations happen that can produce a wide range of timbres. The main problem with FM is that it is not possible to program it ‘intuitively’ without a lot of practice, but its major advantage in the 1970s was that it required very little memory to store a large number of sounds. With huge falls in the cost of storage, this is no longer as crucially important in the 2000s. FM was used in some sound cards and portable keyboards, and like many synthesis techniques, its marketability seems to be influenced by the cycles of fashionability.
Sources of Radio Frequency Radiation
Published in Riadh W. Y. Habash, Electromagnetic Fields and Radiation, 2018
FM radio stations transmit in the 88-108 MHz band. Antennas applied for FM radio stations usually consist of an array of elements built-up vertically and side-mounted on a tower or tower-top pole. In some cases, FM radio antennas may have a relatively large number of elements. The elements are usually spaced about one wavelength apart (around 3 meters) and are fed in phase with power distributed equally among the elements. Sometimes the spacing is one-half wavelength to eliminate the end-fire mode of phase addition, lessening downward radiation. Such antennas are omnidirectional, producing a circular coverage pattern.
Audio compression
Published in David Austerberry, The Technology of Video and Audio Streaming, 2013
Rather than transmitting a stereo audio signal as two separate channels, left and right, the two signals can be matrixed into mid and side signals, much as FM radio uses a mono signal (for compatibility) and a difference signal (modulated on a subcarrier). Since there is a great similarity between left and right for typical audio material, the side or difference signal carries much less information than the mid signal. By this method of processing, the redundancy in information between left and right is eliminated.
Empirical evaluation of real-time traffic information for in-vehicle navigation and the variable speed limit system
Published in Journal of Intelligent Transportation Systems, 2019
Williams Ackaah, Klaus Bogenberger, Robert L. Bertini
RTTI providers can use data from the primary stationary detectors, which in most cases are owned by the government, for broadcasting messages. However, new methods for measuring speeds and travel times such as the floating car data and floating phone data now enable private service providers to offer their services without necessarily having to rely solely on detector data. The data gathered from different sources are then fused. In Germany, service providers process the available data, integrate, and transmit them to the vehicles, smart phones, and so on of the customers through traffic message channel (TMC) technology. The processed traffic information is digitally coded into radio data system (RDS) and transmitted via conventional FM radio broadcast. It can also be transmitted on digital audio broadcasting (DAB) or satellite radio (Wikipedia, 2016). RDS-TMC can embed only a small amount of digital information.
An improved Huffman coding with encryption for Radio Data System (RDS) for smart transportation
Published in Enterprise Information Systems, 2018
C. H. Wu, Kuo-Kun Tseng, C. K. Ng, G. T. S. Ho, Fu-Fu Zeng, Y. K. Tse
RDS is a data broadcast protocol which carries digit data using the sub-carrier of FM radio, and its first version was published by the European Broadcast Union. Figure 1 shows the baseband coding structure of the RDS.